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For less than $500,000, 3 Portland road diets are preventing 37 crashes every year

Posted by on October 10th, 2014 at 2:45 pm

road diet safety

(Data: Portland Bureau of Transportation. Chart: BikePortland.)

A new city study shows the big payoff the city has quietly seen from a few uses of one of the least-understood tricks in traffic engineering: the 4-3 road diet.

Converting four general travel lanes to two plus a turn lane and (in some cases) painted bike lanes have prevented about 525 crashes on three Portland streets — Northeast Glisan from 22nd to 32nd; Southeast 7th from Division to Washington; and Southeast Tacoma from 6th to 11th — during the 16 years studied, the analysis released this week found. The number of traffic crashes on those streets dropped 37 percent.

Traffic volumes on those three streets, meanwhile, fell only by an average 7.7 percent, suggesting that the safety and access improvements weren’t accompanied by major new burdens on drivers’ mobility.

The number of crashes being prevented on each of those streets, of course, continues to rise: by about 37 more every year among the three of them.

Colored bike box and lane SE Hawth. 7th -12.jpg

Southeast 7th Avenue got almost a mile of bike lanes as a result of a 1994-1996 road diet. Colored bike boxes followed in 2008.
(Photo: J.Maus/BikePortland)

Gabriel Graff, operations and safety manager for the city’s Active Transportation Division, said that though the benefits of 4-3 road diets are “counterintuitive,” they ultimately work for a simple reason: people rarely have either a temptation or a reason to pass each other on a city street.

On streets with two lanes in each direction, Graff said, “the people who are going fast have the opportunity to kind of weave between the two lanes. That results in sideswipe crashes.”

Letting left-turning cars sit in the center turn lane, meanwhile, prevents traffic backups and preserves road capacity.

In city jargon, the projects are sometimes referred to as “road reconfigurations.”

Graff said the price of all five road diets considered in the city’s analysis was “in the $100,000 range,” or up to $120,000 or so for projects that added new median islands or other improvements.

“The cost/benefit is really high,” he said. “For the cost of one improved crossing — a median improvement or rapid-flashing beacon that provides a point improvement, you can reduce crashes across 10, 20 blocks.”


In addition to the three road diets listed above, all of them completed between 1997 and 2003, the city looked at the results of two 2013 road diets: Northeast Glisan and Southeast Division, both between 60th and 80th avenues. Though those projects are too recent to show reliable crash data, the city did determine that typical auto speeds fell by 9.8 percent and traffic volumes fell 4.4 percent.

The road diets on inner Glisan, inner 7th and Division all added bike lanes, increasing street capacity and, in the case of 7th, creating one of the central east side’s most important north-south bikeways. The outer Glisan and Tacoma road diets added auto parking.

Graff said road diets have become a standard tool in cities across the country and are now being enshrined in federal policy. Last month, Transportation Secretary Anthony Foxx announced that the Federal Highway Administration is preparing to release a national guide to instituting road diets.

“When we’re on our game, we’re able to combine a really significant safety improvement with some paving maintenance,” Graff said. “So when you’re resource-constrained like we are, that’s a big help.”

You can read the city’s full analysis and dig into some of the numbers behind it on the city’s website.

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47 thoughts on “For less than $500,000, 3 Portland road diets are preventing 37 crashes every year”

  1. Avatar Adam says:

    I love road diets! The central turning lane provides ample space for motorists to pass cyclists, and only having one lane of traffic each direction as opposed to two reduces the stop-gap time for bicyclists and pedestrians (and even motorists) to cross the road.

    And, although I know this is totally only anecdotal, oads on a road diet always *feel* as if the traffic is slower. With two lanes each direction of traffic, there are always one lane of cars racing past the other lane of slower cars, often too fast.

  2. Avatar ktmhz says:

    Wish 52nd had gotten a center turn lane, maybe instead of the parking lane. I can’t recall a day when I have ridden on that road when I haven’t seen someone in a car veer into the bike lane to pass a turning vehicle or to bypass a queue at a traffic light and turn right.

    1. Avatar davemess says:

      It for sure needs a turn lane at SE Steele. Traffic is getting really backed up at that intersection. They have the space (as there is a turn lane at SE Holgate).

  3. Avatar Alex says:

    Can’t wait to see the numbers when Foster Rd goes on a diet.

  4. Avatar Gregg says:

    If I was one of the 37 crash victims saved, I want to thank PBOT for your forward thinking!

  5. Avatar Alex Reed says:

    If we keep reducing motor vehicle use, the road diet targets become almost endless! Powell Blvd. is down 10,000 cars per day over the last decade – from 35,000 to 25,000 ADT at 45th Ave. I believe the threshold for 4-3 road diet is about 21,000 ADT. Come on SE Portland, we can do it! (Next step after that is convincing ODOT but one thing at a time, right?)

    1. Avatar 9watts says:

      Yes! Hawthorne, too!

      Kind of amusing now, looking back and reading the naysayers’ comments –

    2. Avatar Beeblebrox says:

      The best ODOT-owned candidate I can think of is Lombard between Columbia Park and MLK. That section has less than 20,000 cars a day if I remember correctly, and it has a 3-lane cross-section from Columbia Park west to St Johns anyway. It’s a no-brainer.

      1. Avatar Noah Brimhall says:

        This was one of the major recommendations to come out of the Lombard Re-Imagined project. One of the obstacles, as I recall, is that this is a designated route for over-sized freight, but I think that the groupe working on the project found that their contacts at ODOT didn’t think this would be a barrier to a 3-lane configuration. Also, it looks like there is going to be a Walktober event tomorrow about the Lombard Re-Imagined project which might be interesting to folks who have concerns about this stretch of road:

      2. Avatar paikiala says:

        Lombard w/Mississippi, 2008: 821/954 east v westbound peak hour trips.
        1000 is the standard high volume for one lane. It could go higher if bottlenecks were reduced – usually the signal intersections.

    3. Avatar paikiala says:

      Actually, the threshold is not daily traffic, but peak hour. Downtown needs about 1 lane for each 800 peak hour trips, while the outer areas typically use 1,000 trips per lane as the threshold. Sizing roads for the worst times of day is another discussion Examples:

      Glisan at 78th, 2013 peak volumes: 754/694
      Burnside at 17th, 2010: 1089/631
      Holgate at 100th: 768/499

      Not yet
      Glisan at 117th, 975/1017 (on the edge)
      102nd at Wygant, 2010 volumes: 452/518 (doesn’t need 4 lanes)
      MLK at Ankeny, 2010: 1998 peak volume (‘needs’ 2 lanes)
      Grand at Ankeny, 2010: 1361
      Capitol Hwy at Alfred, 2012: 761/929
      Chavez at Brooklyn, 2010: 868/997
      Division at 68th, 2009: 901/747
      Halsey at 152nd: 903/858

  6. Avatar Greg says:

    So bike portland can appreciate road diets as long as the street name doesn’t start with ‘B’ and end with ‘side’?

    1. Avatar David Carlsson says:

      Or start with ‘B” and end with ‘arbur’

    2. Avatar Terry D-M says:

      Now, now…be nice. I know at least further east we support putting Burnside on a diet.

    3. Avatar Alex Reed says:

      Wait, you’re eliding a point here. All of the streets highlighted in the article (except I’m not sure about Tacoma) had road diets with bike lanes added. The complaint on Burnside was that the road diet did not result in bike lanes. And I’m sure Jonathan and almost all the other posters here would say that (non-bike lane road diet) is better than (4-lane road forever). We just also think that (bike lane road diet) is better than (non-bike lane road diet). And we also think that the case for bike infrastructure is so strong and the need so urgent that PBOT should be shoehorning it into any project it can, instead of giving excuses as to why it can’t do bike infrastructure and making projects that are focused on bike infrastructure so weak that they add up to only small improvements (e.g. 20s bikeway).

      1. Avatar 9watts says:


        At the end of the day I think the question for PBOT is: are bikes the most important thing to focus on or are they a sideshow?

        Why should PBOT focus on bikes Über Alles?

        (1) a mile biked saves the city and all of us $$; a mile driven costs us $$;
        (2) biking is healthier, cheaper, safer than driving; those are benefits we could monetize or we could simply appreciate them as improvements in our quality of life;
        (3) we are on the hook to increase bike mode share to what is it? 25%?
        (4) climate change is here; the car is rapidly becoming even more of an Albatross around our necks; anything we can do to ease the transition is money well spent;
        (5) the end of CHEAP oil is also around the corner. Pretending it is not serves no useful purpose.*

        PBOT does not appear to think in these terms, much less draw the kinds of conclusions that seem prudent. Taking bold steps away from automobility takes guts, takes leadership. But the writing is on the wall. What could we possibly have to lose?

        *Oil companies are losing billions right now drilling for the hard to get stuff. The brief blip in US fracked oil and gas is the only net addition to the world’s supply; when that starts to decline, as many suggest it will in the next few years, there’s nowhere to go to make up for the declines in all the world’s so-called conventional oil fields.

        1. Avatar paikiala says:

          Focusing on one mode of transportation is making the same mistake that’s been done for the last 100 years. Haven’t we learned better?

          1. Avatar 9watts says:

            Except that all modes are not created equal. There is no reason bikes couldn’t keep working for 1,000 years. We don’t need ancient sunlight to power them or us. Today’s sunlight is just fine.

          2. Avatar Tom says:

            Focusing on cycling infrastructure actually ISN’T focusing on only one mode of transportation, it’s part of a shift towards a balanced system. Cars have had all of the attention for 50+ years. Focused attention on other modes is essential just to find some sort of balance. But bikes in particular have been all but ignored until the last decade or so…

      2. Avatar Beeblebrox says:

        Tacoma, Glisan (60th to 80th), and Burnside have now gotten road diets without putting in bike lanes. On-street parking is the major reason, though on Burnside it was also due to traffic analysis showing heavy eastbound volumes in the peak. So if people want more bike lanes, we need to have a larger conversation about prioritizing curb space in the city (and a respectful one, not an intense parking vs. bikes fight) and we need to change our traffic Level of Service standards.

      3. Avatar davemess says:

        Alex, correct me if I”m wrong, but aren’t/weren’t you one of the folks saying you wouldn’t use the new bike lanes on SE 52nd? Bike lanes added to Burnside would be pretty much the exact same set up (except you’d be in the door zone on both sides).

        I’m not trying to personally attack you, but I’m just concerned that many seem to be jumping on this Burnside project as being indicative of PBOT’s disinterest in cycling. Would that many people actually use bike lanes on Burnside with Couch and Ankeny right next to Burnside? There are so many on this site clamoring for separated infrastructure, and we have that now for this section (and it works pretty well).
        I would agree that PBOT has messed up a number of projects, but I just find it odd that the Burnside project is really a major one to get people riled up.

        1. Avatar Alex Reed says:

          To be more exact, I said that I wouldn’t use the door-zone side of the 52nd bikeway, and having tried using it, I don’t like it and opt for other options instead. I do use the non-door-zone side of the 52nd bikeway, although I would of course like a wider lane and more separation.

          I do see plenty of other people using both sides of that bike lane. I think the extra foot of space does make it accessible to a slightly wider audience than a 5-foot bike lane (although not wide enough to include me).

          However, I also think protected or buffered bike lanes get you a lot more comfort and riders for your buck. I think there’s space on Burnside for protected bike lanes. One motor vehicle lane each way, center turn line, parking on only one side. Voila!

          Sure, this is magical political thinking on my part given PBOT’s failure to effectively engage, work with, and/or stand up to the business community on 28th ave re: the parking issue. But these are the kind of transformative projects that need to get done in order to change the transportation situation markedly in Portland, and they’re what I’ll be advocating for.

  7. Avatar Jason says:

    It would be interesting to know the net effect of these changes on surrounding roads as well. Did the savings come at the cost of making other arterials less safe?

  8. Avatar John R. says:

    I place this at the feet of Mia Birk and other misguided Portland cycling activists who have stated that bikes should be on side streets instead of places like Hawthorne. Shameful that we have not had more road diets and shameful that they get “credit” when they deserve far less. Less crashes matter. Data matters.

    1. Avatar Nick Falbo says:

      Who do you think put bike lanes on SE 7th Ave in 1994?

      1. Avatar John R. says:

        Hi Nick, Well SE 7th is hardly a major arterial. After Broadway went in, thoughts were that we would see similar treatment on other major streets in Portland. In fact that was the plan. That didn’t happen though and a shift to bike boulevards happened. Fine.

        However Mia has personally spoken out against people biking on Hawthorne and from my perspective we took the easy over the good. Personally, given her business, I think she took the easy to sell over what is right.

        Why isn’t SE Hawthorne one lane with a turn lane and bike lanes? Why after a great bike lane up to Burgerville are you shunted away from the businesses and homes you might want to visit and instead meander through a neighborhood? Maybe you think that’s great, but I don’t. Maybe our bike heroes are better at self promotion and their own businesses over what is right/best for the community. Self interest has a long tradition in American history.

        1. Avatar davemess says:

          bike lanes on Hawthorne (even with a 3 lane configuration) would be pretty skinny though Aren’t Hawthorne lanes already substandard). Parking would have to be addressed to get bike lanes that most people would be happy with.

          1. Avatar John R. says:

            Actually no they would not. Two lanes, one turn lane, bike lanes. It’s not that hard and if you measure the width of the road it could be done. At one time this was actually the plan, smdh.

            1. Avatar GlowBoy says:

              IIRC Hawthorne has 9.5′ wide lanes. That doesn’t leave enough space for safe bike lanes if you reduce it from 4 general travel lanes to 3, especially since long stretches would be in the door zone. I think you still need to reduce parking from one side to make it work.

              That said, I’d love to see it. One problem with the current 4-lane configuration is that maybe 10% or so of drivers still try to go 30+mph, despite the fact that it’s patently unsafe at those speeds. Cutting it to 1 lane each way would do a lot to rein in the blatant speeders.

              Such a road diet would also eliminate the regular impacts that currently happen on Hawthorne when opposing vehicles’ mirrors hit each other (most often when one of those vehicles is a truck or bus that doesn’t actually fit in the lane). I’ve witnessed one of these, and if you keep your eyes open you’ll see there is often debris in the center of Hawthorne from these incidents.

              1. Avatar davemess says:

                The link i attached below shows 9.5′ wide lanes across Hawthorne (I’m guessing the lanes haven’t changed since 1997).

          2. Avatar davemess says:


            Is there a newer plan than this one (which specifically says it does not recommend bike lanes)?

        2. Avatar Nick Falbo says:

          Yes, I do work for Alta, a private firm that has very little to do with what happens here in in the city of Portland, Oregon. (should I add this to all of my posts?)

          I get your frustration with not seeing bike lanes on commercial streets, but I think it’s misguided to imagine that the reason there are no bike lanes on Hawthorne is because Mia Birk once suggested that bicyclists might be better off riding on a bicycle boulevard instead of Hawthorne.

          If you are disappointed in the efforts to improve bicycling conditions in the City of Portland, look to those who have political power and responsibility within the City *today* rather than focusing your energy on someone who used to work there 15 years ago.

          In general, the City of Portland implements bicycle boulevards in house and only hires consultants (such as Kittelson, Alta Planning+Design, CH2M Hill, Nelson\Nygaaard and others) to assist on bike lane projects. Given this, there is no incentive for any of the private firms to promote bicycle boulevards over separated facilities.

        3. Avatar paikiala says:

          Hawthorne at 33rd, 2011: 1127/587 east v. westbound peak trips. The traffic volumes would suggest a Burnside solution, 2+1 travel lanes, with a center turn lane.

      2. Avatar John R. says:

        And Nick, since it looks like you work for Alta, good to call out your own conflicts of interest on this matter. Me? I have none, I don’t even live in Portland anymore.

  9. Avatar gutterbunnybikes says:

    Let me preface this with I live off the section of Division which has recently been dieted and for the most part I like it a lot.

    Though I’m delighted in the reduction of accidents, I don’t really trust the stats on most these studies on road safety. And I feel that there are some assumptions on these stats as presented. There are so many variables at work with these projects that it can be hard if not impossible to pin point what is really at work here. And some of this stuff is pretty important to figure out.

    First other than Tacoma (at 15% – the rest around 6%) the drop in auto traffic falls in line with the average drop in auto traffic that is occurring naturally everywhere across this country right now. So on a whole I doubt that redesigns really reduce traffic by much.

    Second and perhaps the most significant question is how much of the drop in collisions can really be attributed to road design over the drop in the speed limit that I believe accompanied all the thinned streets.

    I have a sneaking suspicion that the infrastructure does little, and most the attributed decrease in incidents has more to do with speed limit changes. Even a drop of 5 MPH is a huge effect on reaction times, stopping distances of an automobile, and the destructive power of a collision.

    How much cheaper would these redesigns have been if the original full outer lanes were shared bike/auto use (commercial greenway style) and the speed limits dropped to 25 mph across the board.

    Sure these projects were on the cheap by PDOT/ODOT standards, but if we could get bicycles full lane access with some legal maneuvering and drop the speed limits significantly and get 80-90% of the incident reductions with a few stickers and signs, we could get the same results for hundreds of dollars per mile.

    1. Avatar Terry D-M says:

      I know living on a stretch of Burnside that has NOT had a diet yet, but will when it gets repaved that just dropping the speed limit will do almost nothing.

      Most of the accidents I have seen occur are during commute time and are due to erratic turns and lane changes. It is obvious if you just watch the behavior. Just signing the speed limit to 30 or even 25 would do very little….it may drop the number of higher speed accidents at the off-times when the roadway is not congested…particularly at traffic lights…. but these types of accidents are not anywhere near as common.

      I would support the outer lane becoming Bikes and Buses ONLY, but not with cars. The configuration you mention, at least on Burnside, would be more dangerous than it is now. You could say “well if there was more enforcement”……but Traffic headquarters is just 3/4 of a mile down the street, and it has never slowed anyone down that I can tell.

    2. Avatar Beeblebrox says:

      Actually, research has consistently shown that simply changing speed limits without changing roadway design does absolutely nothing to change driver behavior. That’s why speed limits are set based on observed or expected speeds, rather than on how fast we would like people to drive. Think about it–if you were driving on 82nd Ave as it is now, but they changed the speed limit signs to 25, would you actually drive 25? Probably not. Design is what determines speed, so the infrastructure is what is really important here, not speed limits.

      1. I won’t let your argument stop me from wanting a blanket speed limit change down to 20 mph or less in our neighborhoods. It’s just crazy that people think it’s okay to go 25 mph on streets where children are supposed to be playing.

        Credit where it’s due, these roads diets work.

      2. Avatar davemess says:

        There is also the lack of police enforcement in this town.

        1. Avatar Alex Reed says:

          And the State of Oregon ban on 24-7 automated speed enforcement, which is used cheaply and effectively in other places.

      3. Avatar paikiala says:

        Agreed, but if 82nd was one lane each direction and the speed was posted 25, I’m pretty sure the average 85th would decrease. Safe Systems is a holistic approach to reducing crash severity. The primary speed reducing benefit of a road diet is the elimination of legal, and unrestricted, passing opportunites two lanes in the same direction provides. Even without changing the layout of 82nd, if the new speed was more rigorously enforced, the speeds are likely to drop.

    3. Avatar paikiala says:

      I agree that total numbers can be misleading. The better before and after measure is crash rate, and in the case of corridors, crash rate per mile. This would compare the number of crashes relative to the number of users, so if the number of crashes went down as well as number of users, then the crash rate may not have changed at all. This would still only be one side of the story. The other side is the crash severity and how it may, or may not, have changed. Reducing total number of crashes is only a proxy to the real goal, reducing the number of severe injuries and fatalities.

  10. Avatar James says:

    I’m all for road diets, but it’d be nice if they were accompanied by diverters to keep embittered motorists from using the bikeways.

    Clinton hardly deserves the distinction of “bikeway” anymore.

    1. Avatar paikiala says:

      Functional classification does not equal level of implementation. Bikeway is a label, Neighborhood Greenway is a standard, and Clinton has not yet been built to that standard.

  11. Avatar Bjorn says:

    It would be nice if there were some way that the city could recover the money they have saved insurance companies with these road diets.

    1. Avatar Dan says:

      Insurance companies could lobby for road diets, if they stand to profit from them.

  12. Avatar Tom Kloster says:

    Per Alex Reed, there’s a chance that the groundless (and over-reaching) state ban on automated traffic enforcement will get a serious revisit in the next legislative session for the first time in many years:

    Even better, there’s support from City Hall for the bill — but it will be a heavy lift and require a lot of activism.

    This would be a huge step forward in actually enforcing posted speeds — though I also agree that Portland has no surface streets that warrant travel (or posted) speeds above 30 mph, nor is the safety risks for cyclists and pedestrians worth the few minutes drivers theoretically “save” by racing through our community, petal to the metal.

    I’ve lived on North Willamette Boulevard for 22 years, so have watched too many tragedies and near-tragedies — we do need to finally put a stop to speeding cars in this community.

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